/*
* Insert a jump offset at 'offset' to complete an instruction
* (the jump offset is always the last component of an instruction).
* The 'skip' argument must be computed relative to 'offset',
* -without- taking into account the skip field being inserted.
*
* ... A B C ins X Y Z ... (ins may be a JUMP, SPLIT1/SPLIT2, etc)
* => ... A B C ins SKIP X Y Z
*
* Computing the final (adjusted) skip value, which is relative to the
* first byte of the next instruction, is a bit tricky because of the
* variable length UTF-8 encoding. See doc/regexp.rst for discussion.
*/
DUK_LOCAL duk_uint32_t duk__insert_jump_offset(duk_re_compiler_ctx *re_ctx, duk_uint32_t offset, duk_int32_t skip) {
duk_small_int_t len;
/* XXX: solve into closed form (smaller code) */
if (skip < 0) {
/* two encoding attempts suffices */
len = duk_unicode_get_xutf8_length((duk_codepoint_t) duk__encode_i32(skip));
len = duk_unicode_get_xutf8_length((duk_codepoint_t) duk__encode_i32(skip - (duk_int32_t) len));
DUK_ASSERT(duk_unicode_get_xutf8_length(duk__encode_i32(skip - (duk_int32_t) len)) == len); /* no change */
skip -= (duk_int32_t) len;
}
return duk__insert_i32(re_ctx, offset, skip);
}
/* Encode to extended UTF-8; 'out' must have space for at least
* DUK_UNICODE_MAX_XUTF8_LENGTH bytes. Allows encoding of any
* 32-bit (unsigned) codepoint.
*/
duk_small_int_t duk_unicode_encode_xutf8(duk_ucodepoint_t cp, duk_uint8_t *out) {
duk_uint_fast32_t x = (duk_uint_fast32_t) cp;
duk_small_int_t len;
duk_uint8_t marker;
duk_small_int_t i;
len = duk_unicode_get_xutf8_length(cp);
DUK_ASSERT(len > 0);
marker = duk_unicode_xutf8_markers[len - 1]; /* 64-bit OK because always >= 0 */
i = len;
DUK_ASSERT(i > 0);
do {
i--;
if (i > 0) {
out[i] = (duk_uint8_t) (0x80 + (x & 0x3f));
x >>= 6;
} else {
/* Note: masking of 'x' is not necessary because of
* range check and shifting -> no bits overlapping
* the marker should be set.
*/
out[0] = (duk_uint8_t) (marker + x);
}
} while(i > 0);
/*
* Insert a jump offset at 'offset' to complete an instruction
* (the jump offset is always the last component of an instruction).
* The 'skip' argument must be computed relative to 'offset',
* -without- taking into account the skip field being inserted.
*
* ... A B C ins X Y Z ... (ins may be a JUMP, SPLIT1/SPLIT2, etc)
* => ... A B C ins SKIP X Y Z
*
* Computing the final (adjusted) skip value, which is relative to the
* first byte of the next instruction, is a bit tricky because of the
* variable length UTF-8 encoding. See doc/regexp.rst for discussion.
*/
DUK_LOCAL duk_uint32_t duk__insert_jump_offset(duk_re_compiler_ctx *re_ctx, duk_uint32_t offset, duk_int32_t skip) {
#if 0
/* Iterative solution. */
if (skip < 0) {
duk_small_int_t len;
/* two encoding attempts suffices */
len = duk_unicode_get_xutf8_length((duk_codepoint_t) duk__encode_i32(skip));
len = duk_unicode_get_xutf8_length((duk_codepoint_t) duk__encode_i32(skip - (duk_int32_t) len));
DUK_ASSERT(duk_unicode_get_xutf8_length(duk__encode_i32(skip - (duk_int32_t) len)) == len); /* no change */
skip -= (duk_int32_t) len;
}
#endif
#if defined(DUK_USE_PREFER_SIZE)
/* Closed form solution, this produces smallest code.
* See re_neg_jump_offset (closed2).
*/
if (skip < 0) {
skip--;
if (skip < -0x3fL) {
skip--;
}
if (skip < -0x3ffL) {
skip--;
}
if (skip < -0x7fffL) {
skip--;
}
if (skip < -0xfffffL) {
skip--;
}
if (skip < -0x1ffffffL) {
skip--;
}
if (skip < -0x3fffffffL) {
skip--;
}
}
#else /* DUK_USE_PREFER_SIZE */
/* Closed form solution, this produces fastest code.
* See re_neg_jump_offset (closed1).
*/
if (skip < 0) {
if (skip >= -0x3eL) {
skip -= 1;
} else if (skip >= -0x3fdL) {
skip -= 2;
} else if (skip >= -0x7ffcL) {
skip -= 3;
} else if (skip >= -0xffffbL) {
skip -= 4;
} else if (skip >= -0x1fffffaL) {
skip -= 5;
} else if (skip >= -0x3ffffff9L) {
skip -= 6;
} else {
skip -= 7;
}
}
#endif /* DUK_USE_PREFER_SIZE */
return duk__insert_i32(re_ctx, offset, skip);
}
